Turkey has summoned the Saudi ambassador to request the kingdom's "full cooperation" in an investigation into the disappearance of journalist Jamal Khashoggi, who Turkish officials say was killed while visiting the Saudi Consulate in Istanbul.

The 59-year-old Khashoggi went missing last Tuesday while visiting the consulate for paperwork to marry his Turkish fiancee.

A Turkish official said the Saudi ambassador met with Deputy Foreign Minister Sedat Önal on Sunday at the ministry. The Turkish private NTV television said Ankara requested permission for Turkish investigators to search the consulate building in Istanbul.

Turkish officials told news agencies over the weekend that they believed Khashoggi had been killed inside the Saudi consulate in Istanbul, and President Tayyip Erdoğan said he was personally following the case.

On Monday, a Turkish official also said Saudi Arabia's envoy to Ankara had been summoned to the foreign ministry for a second time on Sunday and had been asked by Turkish diplomats to be "in full coordination" on the matter.